Semiconductor - PN Diode

• When electron flow in one direction in semiconductor, the holes flows in opposite direction.
• At low temperature Semiconductor behaves like Insulator (Eg. Germanium-Ge, Silicon-Si)
• Temperature Increases, Energy gap decreases
• Current per unot area is called current density.
• Ability of harge carrier to move inside the semiconductor is called Mobility.
• As temperature increases Mobility Decreases.
• As temperature Increases Conductivity Increases, Because conductivity depends on charge carrier.
• Pentavalent impurities are Donor impurities as it donate the electron for conduction for conductivity.
• In N-type majority charge carrier are Holes and minority charge carrier are Electrons
• The diode can b used as voltage controlled switch. i.e., OFF for Reverse biased voltage and ON for Forward Forward biased voltage
• Valance Electrons are the electrons present in the outermost orbit
• The elemet that doesnot have three valence eletrons is Galium
• The element have 3 valance electrons is- Boron, Alluminium, Germanium
• The element having four valence electron is silicon and Germanium.
• The forbidden gap for silicon is 1.12ev
• The forbidden energy gap for Germeniuim is 0.72ev
• The resistivity of a semiconductor has a negative temperature coefficient of a resistance
• The donor impurity element is Phosphorous,
• The acceptor impurity element is Gallium
• The element which doesnot have 5 valence electron is Gallium
• The element which has 5 Valence electron is Antimony,Arsenic, Phosphorous
• The forbidden bandgap of the semiconductor material Decreses with increase in temperature.
• Indium is not a semiconducting material
• Gallium Arsenide, Germenium, Silicon are semiconductors
• Capacitor has the ability to act as an open circuit for DC and short circuit for AC of high frequency
• The static resistance if a diode is its opposition to dc current flow
• when the reverse bias is applied to a junction diode, it raises the potential barrier
• Dopng of semiconductor is the process of adding certain impurities to the semiconductor material in controlled amount
• Refering the energy level diagram of semiconductor materials, the width of the forbidden band gap is about 1ev.
• A PN junction diode had low resistance in the forward direction
• If a PN junction diode is not biased, the junction current at equillibrium is zero as equal number of carriers cross the barrier
• In a PN junction the potential barrier is due to the charges on wither side of the junction which consists of fixed donor and accepto ions
• In a PN junction, the region containing the uncompensated acceptor and donor ions is called Depletion region
• In a forward biased PN junction diode, the Positive terminal of the battery is connected to the N-Side and Negative terminal to the N-Side
• when PN junction is forward biased - Electrons in N-Region are injected into the P-region. i.e., Holes in P-region are injected into the N-region
• When we apply reverse bias to a junction diode, it raises the potential barrier
• Under normal operating voltage, the reverse current in a silicon diode is about 1uA
• The depletion region is PN diode is due to Reverse Biasing
• When a diode is forward biased, Barrier potential Decreases.
• For a Silicon PN junction, the maximum value of barrier potential is 0.7V
• The resistivity of a semiconductor depends on the length of the semiconductor
• When holes leave the P-material to fill electrons in the N-material this Process is called Diffusion
• The depletion region in a PN diode is due to Reverse Biasing
• When a diode is forward biased, the barrier potential decreases
• In a semiconductor diode V-I relationship is such that current increases exponentially with voltage
• The capacitance appearing across a reverse biased smiconductor junction decreases with increase in bias voltage.
• Zener Brakdown occurs due to Rupture of covalent bonds
• A breakdown which is caued by commulative multiplication of carriers through field induced impact ionization occurs in Avalanche Diode
• Zener diode is usually operated in Reverse Bias Mode
• For highly Doped diode - Zeer Breakdown is likely to take place
• Zener diode is used for voltage stabilization
• In Zener and Avalanche breakdown diodes, the current flow is due to minority carriers.
• The breakdown that occurs in the reverse biased condition in a narroe junction diode is Zener Breakdown
• The breakdown that occurs in the reverse biased condition in a wider junction diode is Avalanche Breakdown
• A Zener Breakdown diode has a Positve Temperature Coefficient
• An Avalanche Breakdown diode has a Negative Temperature Coefficient
• In Avalanche Multiplication, Disruption of covalent bond occur by colliion
• Zener diode is a Constant Voltage Device
• There are two semiconductor Diodes A and B, One of them is Zener whereas other is Avalanche, their rating are 5.6v and 24v respectively, then A is Zener and B is Avalanche
• The diode used in Voltage Regulator is Zener Voltage.

True (or) False:

• Silicon and Germanium with Valance electron of 4 - (True)
• Hole Current is the movement of negative charges in the opposite direction from the electron flow ( False)
• Doping with the Phosphorous makes silicon P-type with majority electron charges and minority hole charge (False)
• Hole curret into an electrode is considered as a posite direction of current (True)
• The internal barrier potential at PN junction for silion is appoximately 9v (False)
• Atoms of the impurity element in a doped semiconductor provide fixed ion charges (True)
• A depletion layer consists of free charge carriers (False)
• A N-type semiconductor has a free electron, while P-Type has hole charge. (True)
• A hole has the same amount of positive charge as a proton, equal to an electron but with opposite polarity (True)
• The proton is stable charg in the nucleus that is not free to move (True)
• A hole is positive charge outside the nucleus present only in semiconductor becaue of unfilled covlent bond (True)
• The forward current of PN Juntion can be controlled to provide amplification (True)
• Gallium is generally used for germanium as donor impurity element (False)
• Phosphorous inits purest form acts as an Intrinsic semiconductor (True)
• Gallium is generally used as an acceptor impurity for germanium (True)
• A Zener diode operates in reverse biased region (True)
• A zener diode is used a a rectifier (False)
• The diode current equation I0 = I (E^v/uVT - 1) - (False)
• To obtain N-type semiconductor, the impurity added to a pure semiconductor is pentavalent (True)
• A semiconductor has a Negative Temperature Coefficient of resistance (True)
• In the reverse biase region, the reverse saturation current of a silicon diode rises for evry 10*C in temperature (True)
• When PN junction is biased in the forward direction majority carrier in each region are injected into the other region (True)